Many satellite communication systems are designed to operate for many years. In order to maintain reliability and prolong the working life of a satellite payload, the payload may be equipped with spare or redundant units that are designed to be switched into a signal path when a primary unit fails. By way of example, a payload may include ten primary low-noise amplifiers and two spare low-noise amplifiers. When one of the primary low-noise amplifiers fails, one of the two spare low-noise amplifiers may be switched into a signal path of the failed low-noise amplifier.
Switching a spare unit into the signal path of a failed primary unit may involve sending a radio frequency (RF) command to an electromechanical switch. For instance, the electromechanical switch may have two positions: in a first position, the electromechanical switch may link a primary unit to a signal path; and in a second position, the electromechanical switch may link a spare unit to the signal path. If the primary unit fails, an RF command may be sent to the electromechanical switch, causing the switch to transition to the second position.
When multiple primary units and multiple spare units are included, a redundancy ring may be used to allow for replacing a primary unit with a spare unit. FIG. 1 conceptually illustrates an example configuration of part of a conventional communications satellite payload. As shown in FIG. 1, the communications satellite payload may include an input redundancy ring switch 102 that connects a plurality of input paths 104 to a plurality of nominal paths 106. The plurality of input paths 104 includes four primary input paths and two spare input paths. Each of the four primary input paths may lead to a corresponding primary input unit and each of the two spare input paths may lead to a corresponding spare input unit. The input redundancy ring switch 102 may include six switches, each of which can be positioned in a nominal position, an up position, or a down position. Initially, the six switches may each be positioned in the nominal position, such that a first switch S1 links “input 1” to “nominal path 1”, a second switch S2 links “input path 2” to “nominal path 2”, and so forth. As further shown in FIG. 1, the communications satellite payload may also include an output redundancy ring switch 110 that connects the plurality of nominal paths 106 to a plurality of output paths 112.
In operation, when one or more primary input units fail, individual switches of the input redundancy ring switch 102 are shuffled up or down to switch signals from the spare units into the plurality of nominal paths. For example, as shown in FIG. 2, a fourth switch S4 and a fifth switch S5 may be switched to the up position, such that “input 4” is switched into “nominal path 3” and “spare 1” is switched into “nominal path 4”. In addition, the first switch S1 and a sixth switch S6 may be switched to the down position, such that “input 1” is switched into “nominal path 2” and “spare 2” is switched into “nominal path 1”.
When using a redundancy ring switch, such as the input redundancy ring switch 102 of FIGS. 1 and 2, the individual switches are controlled using special commands. In particular, the individual switches are controlled individually by sending high voltage pulses to the switches, with the pulse causing the switch to transition to a different position.
Moreover, when shuffling the switches of a redundancy ring switch to switch a spare path into a nominal path, a disruption of service occurs on other nominal paths. For instance, as discussed above, when replacing “input 2” and “input 3”, disruption occurs on not only “nominal path 2” and “nominal path 3”, but also “nominal path 1” and “nominal path 4”. Specifically, “nominal path 1” is disrupted when “input 1” is switched to “nominal path 2”, and “nominal path 4” is disrupted when “input 4” is switched to “nominal path 3”.
In addition, individual switches of a redundancy ring switch can block each other, limiting the number of spare input paths that can be switched in. For example, referring back to FIG. 2, even if the input satellite payload included a third spare between “spare 1” and “spare 2” (not shown) and the input redundancy ring switch 102 included a corresponding seventh switch between the fifth switch S5 and the sixth switch S6 (not shown), the input redundancy ring switch 102 would be unable to switch the third spare into any of the plurality of nominal paths 106. This is because the switches adjacent to the seventh switch could not be shuffled up or down any further. This problem could be remedied by adding many more switches to the redundancy ring (e.g., adding a pair of switches every two nominal paths). However, adding more switches to a redundancy ring switch is costly and increases the weight of the payload.